As digital still cameras and digital video cameras (hereinafter collectively referred to as “digital cameras”) have become in widespread use in recent years, a storage medium such as a memory and a hard disk stores a large volume of digital data (images), such as still images and moving images, captured with the digital cameras. Since a storage medium thus stores a large number of images, it is becoming increasingly difficult to, for example, (i) retrieve, from the images stored, an image of a desired person or (ii) classify the images by a person in each image.
To retrieve a desired image from numerous images or classify such numerous images, so-called facial recognition can be carried out, in which a registered face image is matched with a captured face image (biological information) so as to determine whether a person in the registered face image is identical to a person in the captured face image.
Facial recognition, however, has a problem that matching accuracy decreases over time because the face of a person changes over time in actuality due to aging although a registered image of the face does not change.
To solve this problem, Patent Literature 1 discloses a technique of reducing an influence of such a change due to aging by (i) generating, from an image inputted in matching and an image stored, an image to be newly registered, and (ii) automatically updating the stored image to the newly generated image.
Patent Literature 2 discloses a technique of increasing recognition accuracy by using a plurality of biological information items in recognition.
Patent Literature 3 discloses a technique of deleting, from a storage medium, an image of low importance which image has been stored in the storage medium for an extended period of time since the image was registered or last used in matching.
Patent Literature 4 discloses a technique of increasing recognition accuracy by determining features for use in facial recognition which features correspond to a period between a time at which a face image was registered and a time at which an image of the face was captured.
Patent Literature 5 discloses a technique of carrying out recognition in accordance with actuality by using, in recognition, biological recognition data (image data) captured at a plurality of past times.
Patent Literature 6 discloses a technique of carrying out delta compression of a captured face image for storage on the basis of a difference between (i) the captured face image and (ii) a similar face image exhibiting a similarity which is not below a predetermined reference value.